High-frequency coupling device



w G TULLER 2,433,074 HIGH-FREQUENCY COUPLING DEVICE Flled July 2 1943mmvroa 0mm! 63 ELLE/ BY W v 'flTTX Dec. 23, 1947.

Patented Dec. 23,. 1947 HIGH-FREQUENCY COUPLING DEVICE WilIi'amGi'Tullentwatertowii; Ma's'sl', assignsfic Massl ai'corporation ofR'ayth'eo'm' Manufacturing Company, Newton,

' Delaware Application J uly. 2 1943, -Serial= N o2 493,224 r 4 cl'aimsr(Cl. 178 -44) This inventionrelates to" guided" electromag netic'wavetransmission, and more particularlyto Another object is :to :producesucha-"coupling by.

asimple and. .compacttstructure.

The:- foregoing; and other. objects ;of. this .in-

vention will be best understoodfrom thejfol lowing descriptionof.an.exemplification-thereof,

reference: being hadito; the: accompanying draw-- ingI wherein:

Fig. 1 isasection through my novel coupling."

system taken alongline .l-l of Fig. 2; and

Fig. Zis. a. section: taken along line.2-2-- of Fig; 1..

The couplingsystem. shown comprises a-icoaxial conductor. transmissionline consisting of a tubular conductor l having-a neutral conductor 2,said:

transmission line being coupled-to ahollow dielectric waveguideThemembersl Land 3 are: formed :01 highly conducting material,- such ascopper or brass. The wave guide 3 is preferably of rectangularcross-section having a long side Aland a short side-: Oneend'of thetubular conductor I is joined to one long side 4 of the wave guide3whichis provided with an opening therein-substantially of' the-size ofthetubular conductor l through'which the-conductor 2pro- J'ects for 'asubstantial distanceinto the wave guide 3.

When electromagnetic waves of sufficiently high frequency aretransmittedalong the coaxial conductor transmissionlin'e, the 'ab'ovecoupling ar rangement will excite'tlie-wave'guide 3 in what is knownasthe-'IEt'n mode; and such waves will be propagated down through the waveguide. The TEo,1 mode is that=mode"in' which the electric vector of thepropagatedcwave is always transverse to the direction of propagation ofthe wave in the wave guide. There is a single maximum of fielddistributionalong'one side of the wave guide, and no such maximumialongthewother' sldeofi said wave guide: Inzrthearrangements which I haveillustrated, the single maximum-will occur alongthe longlside ofthe'waveguide: The TEo,1 mode is the simplest and most commonly 2f used? mode of'exbitation of "wave guides of this' typ r N Inordr for thecenergylofthewave which is propagated along such a system to be efiectively' andefiiciently transferred from the coaxial conductor transmission line tothe Wave guide, it is desirable that there be no reflections atthe pointof coupli-n'gbetween these two 'sy'stemss For 'this pose tlie impe danceOi the -conductor wmen extends into the wave guide 3 and formsaprobeshould be matched to the impedance of the coaxial conductortransmission line. I have found that if-thetprobeend of the conductor2-is terminated by a partial spherical member 6, that i s, a sphericalmember which iswflattened in the plane..where it meets the probe end orsaid conductor 2; b'ear'ingthe proper relationship both to: the:diameter of. the conductor 2" andto-th'eim side. diameter. of theconductor l, the impedance ofthecoaxial conductor transmission line canbe matched with the-impedance of the probe and thus produce the desired.refiectionless coupling.

Insuoh an arrangement also a-reflecting platel is locatedin the waveguide S at the proper distance behind th'e probe-so asto form a resonantchamber termination for said wave guide.

I have found that using. the following notation: S =diameter of partialsphere 6 A=diameter of conductor 2, Binner diameter ofecondu'ctor lThus, for exam'ple, in a coupling arrangement in which theinnerdi'ameterofthe conductor I was .81 2-in'ch th'e diameter of theconductor 2 was .375

inch and the diameter of the partial sphere 6 was-.4375 inch,substantiallyno reflection occurredat the coupling point.

ternal cross-section, and the :probe extended into the wave guide .965inch.

A consideration of. the above equation shows that as: th ratioofB/A;increases,-the ratio of S/A decreases. Thus, iforexampleywhere theinternal-diametenof theconductonl was 1.527 inches and the diameter ofthe conductor 2 was .625 inch, the diameter-of the partial-sphere 6* waslikewise '.625 inch. In order for-proper open 1 ation,-thepartial sphere1 6 should be attached to the conductor 2- so i that the section throughthe 1 partial sphere in the plane where-it is attached-to the conductorshould be of the same size as the In-this case thewave guide was 1.344inches by 2.834 inches in in'-' cross-section of the conductor. Thus thelast example cited represents a limiting case in which the member 6 is ahemisphere. If the ratio of B/A were to be increased beyond thatindicated, the ratio of S/ A would be less than one, and therefore thecondition of matched section of the partial sphere and the cross-sectionof the conductor would not ordinarily be obtained. However, forconditions of this kind I have found that the end of the conductor 2 asit approaches the partial sphere 6 may be gradually decreased indiameter so as to afford at least a one-to-one ratio between thediameter of the partial sphere and the reduced diameter of the end ofthe conductor 2.

Coaxial conductor transmission lines and dielectric wave guides, such asI have described above, are usually designed to carry electromagneticwaves of approximately a predetermined wave length in the wave guide,which wave length may be represented by A. In Fig. 1 I hav designatedthe distance between the reflecting surface of the plate 1 and thecenter of the probe as L. Theoretical considerations have indicated thatL should be about I have found, however, that proper operation issecured in my arrangement when L is approximately I have found thatcoupling systems constructed in accordance with the foregoing principleshave enabled the transmission of substantially increased quantities ofelectromagnetic power therethrough. Also I have found that such acoupling arrangement remains matched in its impedance to the impedanceof the coaxial conductor transmission line over a relatively substantialfrequency variation in the electromagnetic wave without furtheradjustment. It is to be understood that the numerical values ofparticular systems which I have listed above are given merely by Way ofexample, and it is further understood that the principles of myinventionmay be applied to a wide variety of coupling systems.

What is claimed is:

1. A coupling system comprising a coaxial conductor transmission linehaving an outer conductor surrounding an inner conductor, a hollow waveguide, said inner conductor extending into said hollow wave guidethrough an opening in a side wall of said wave guide and forming aprobe, said probe being placed in a transverse electric mode-excitingrelationship With respect to said hollow wave guide, said outerconductor being connected to said wall, said probe terminating in amember comprising a portion of a sphere, the diameters of said member,said probe and said outer conductor bearing approximately the relationwhere S is the diameter of the member, A is the diameter of the probeand B is the inner diameter of the outer conductor.

2. A coupling system comprising a coaxial conductor transmission linehaving an outer conductor surrounding an inner conductor, a hollow waveguide, said inner conductor extending into said hollow wave guidethrough an opening in a wall of said wave guide and forming a probe,said probe being placed in a, transverse electric modeexcitingrelationship with respect to said hollow wave guide, said outerconductor being connected to said wall, said probe terminating in aspherical member which is flattened in the plane where it meets saidprobe, the area of the flattened portion being equal to thecross-sectional area, of said probe, and an electromagneticwave-reflecting plate disposed across said wave guide at one side ofsaid probe and spaced from the center of said probe a distanceapproximately equal to onesixth of the wave length of theelectromagnetic wave which said wave guide is adapted to transmit.

3. A coupling system comprising a coaxial conductor transmission linehaving an outer conductor surrounding an inner conductor, a hollow waveguide, said inner conductor extending into said hollow wave guidethrough an opening in a side wall of said wave guide and forming aprobe, said probe being placed in a transverse electric mode-excitingrelationship with respect to said hollow wave guide, said outerconductor being connected to said wall, said probe terminating in amember comprising a portion of a sphere, the diameters of said member,said probe and said outer conductor bearing approximately the relation .where S is the diameter of the member, A is the diameter of the probeand B is the inner diameter of the outer conductor, and anelectromagnetic wave-reflecting plate disposed across said wave guide atone side of said probe and spaced from the center of said probe adistance approximately equal to one-sixth of the wave length of theelectromagnetic wave which said inner guide is adapted to transmit.

4. A coupling system comprising a coaxial conductor transmission linehaving an outer conductor surrounding an inner conductor, a rectangularhollow wave guide, said inner conductor extending into said hollow waveguide through an opening in a side wall of said wave guide and forming aprobe, said probe being placed in the TEo,1 mode-exciting relationshipwith respect to said hollow wave guide, said outer conductor beingconnected to said wall, said probe terminating in a member comprising aportion of a sphere, the diameters of said member, said probe and saidouter conductor bearing approximately the relation REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,147,717 Schelkunoff Feb. 21,1939 2,307,012 Barrow Jan. 5, 1943 2,316,151 Barrow Apr. 13, 1943Certificate of Correction Patent No. 2,433,074. December 23, 1947.

WILLIAM G. TULLER It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows: Column 2, line 42, for 1.344 read 1.384; and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the case in the Patent Office.

Signed and sealed this 9th day of March, A. D. 1948.

THOMAS F. MURPHY,

Assistant aommzsswner of Patents.

